You get a glance of the Loop from their rooftop. Plus the store. That's it.
No you can't, the Apple Park is a closed campus.
I can't enter Apple Park and I can't see it very well from the visitor center.
The later, just an apple store with a simulation of the grounds. If you're an apple fan and are in the area then go, don't go too far out of your way.
Just the retail store. No Apple Park access. But it's right next to the park.
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